function constructor(){
  this.now = new Date();
  this.nowYear = this.now.getYear(); //当前年 
  this.nowMonth = this.now.getMonth(); //当前月 
  this.nowDay = this.now.getDate(); //当前日 
  this.nowDayOfWeek = this.now.getDay(); //今天是本周的第几天 
  this.nowYear += (this.nowYear < 2000) ? 1900 : 0;
}
//格式化数字
function  formatNumber(n) {
  n = n.toString()
  return n[1] ? n : '0' + n
}
//格式化日期
function  formatDate(date) {
  let myyear = date.getFullYear();
  let mymonth = date.getMonth() + 1;
  let myweekday = date.getDate();
  return [myyear, mymonth, myweekday].map(this.formatNumber).join('-');
}
//获取某月的天数
function getMonthDays(myMonth) {
  let monthStartDate = new Date(this.nowYear, myMonth, 1);
  let monthEndDate = new Date(this.nowYear, myMonth + 1, 1);
  let days = (monthEndDate - monthStartDate) / (1000 * 60 * 60 * 24);
  return days;
}
//获取本季度的开始月份
function getQuarterStartMonth() {
  let startMonth = 0;
  if (this.nowMonth < 3) {
    startMonth = 0;
  }
  if (2 < this.nowMonth && this.nowMonth < 6) {
    startMonth = 3;
  }
  if (5 < this.nowMonth && this.nowMonth < 9) {
    startMonth = 6;
  }
  if (this.nowMonth > 8) {
    startMonth = 9;
  }
  return startMonth;
}